Microelectromechanical systems (MEMS) is the technology of very small devices. FIG. 1 shows a prior art MEMS device that includes a scanning platform.
MEMS device 100 includes fixed platform 102, scanning platform 140 and scanning mirror 116. Scanning platform 140 is coupled to fixed platform 102 by flexures 110 and 112, and scanning mirror 116 is coupled to scanning platform 140 by flexures 120 and 122. Scanning platform 140 has a drive coil connected to drive lines 150.
In operation, current introduced into the drive coil causes the scanning platform to move relative to the fixed platform when in the presence of a magnetic field. Control systems are typically employed to control the movement of the scanning platform relative to the fixed platform.
MEMS device 100 is typically mounted to an assembly. If the MEMS device and the assembly to which the MEMS device is mounted do not exhibit identical thermal expansion behavior, or if they are not exactly co-planar, stress forces may be transmitted to the MEMS device due to expansion, contraction, die warpage, or the like. These stresses can be transmitted to the flexures supporting the scanning platform and/or the scanning mirror, thereby changing their stiffness characteristics. For example, compressive stresses due to material shrinkage at different rates may reduce the bending stiffness of flexures 110 and 112, thereby changing their resonant behavior. Control system design may become more complicated as a result.